python 快速比较两个文件的不同

import difflib

a = open('./1.txt', 'U').readlines()
b = open('./2.txt', 'U').readlines()
diff = difflib.ndiff(a, b)
print(diff)
for i in diff:
    print(i)
    # if i.startswith('+'):
    #     print(i)

#or
print(set(b)-set(a))